The present invention relates to a method of picking up semiconductor chips formed by dividing a semiconductor wafer along predetermined cutting lines.
In the production process of a semiconductor device, a circuit such as an IC or LSI is formed in a large number of areas arranged in a lattice form on the surface of a substantially disk-like semiconductor wafer and each area having the circuit formed therein is diced along predetermined cutting lines to produce a semiconductor chip. To improve the heat radiation property of the semiconductor chip, the thickness of the semiconductor chip is desirably made as small as possible. To enable the downsizing of portable telephones, smart cards, personal computers and the like in which a large number of semiconductor chips are used, the semiconductor chip is desirably formed as thin as possible. To this end, before the semiconductor wafer is divided into semiconductor chips, the back surface of the semiconductor wafer is ground to a predetermined thickness. As a technology capable of further reducing the thickness of the semiconductor chip to be divided, there has also been developed a processing method so-called xe2x80x9cpre-dicingxe2x80x9d which comprises forming dicing grooves having a predetermined depth in the surface of the semiconductor wafer before the grinding of the back surface of the semiconductor wafer, and grinding the back surface of the semiconductor wafer until the dicing grooves are exposed to divide the semiconductor wafer into semiconductor chips.
Since a protective tape mounted on a ring frame is affixed to the semiconductor wafer before it is divided into semiconductor chips in the above-described manner, the obtained semiconductor chips are not separated from one another by the action of the protective tape and held on the protective tape mounted on the ring frame. A plurality of semiconductor chips thus obtained are sent to a pick-up step such as a die bonder or the like while they are held on the protective tape mounted on the ring frame. Heretofore, in the pick-up step, the semiconductor chips have been pushed up by a thrusting pin while the above protective tape is adsorbed by a back-up holder to separate the semiconductor chips from the protective tape, and the separated semiconductor chips have been picked up by a collet and stored in a predetermined package or a conveying tray.
The semiconductor chip formed thin as described above is, however, liable to be broken due to reduced rigidity and may be often damaged when they are pushed up by the thrusting pin in the above pick-up step, resulting in reduced yield. In the above conventional pick-up method, even when a plurality of semiconductor chips formed by dividing the semiconductor wafer can be picked up and transferred to a conveying tray en bloc, they must be picked up one by one, thereby making it impossible to improve productivity.
Meanwhile, the applicant has proposed in Japanese Laid-open Patent Applications 25881/2000 and 158334/2000 (JP-A 2000-25881 and JP-A 2000-158334) a tray comprising an elastic adhesive pad with innumerable pores in the surface for adhesively holding a plate-like workpiece, making use of negative pressure produced when the pores are crushed by restoration force generated by elasticity and adhesion, in order to enable a thin plate-like workpiece having low rigidity to be carried easily. When the plate-like workpiece adhesively held on the tray comprising the elastic adhesive pad is to be separated from the elastic adhesive pad after it has been carried to a predetermined processing step, negative pressure in the pores formed in the surface of the elastic adhesive pad is reduced by supplying air to the elastic adhesive pad, whereby the plate-like workpiece is separated from the elastic adhesive pad. However, in the above method of supplying air to the elastic adhesive pad, it is difficult to supply air to all the pores formed innumerably in the surface of the elastic adhesive pad and considerable suction force may often remain in the elastic adhesive pad. In this case, when the plate-like workpiece is very thin and has low rigidity like a semiconductor wafer or semiconductor chip, it is damaged at the time of separation from the elastic adhesive pad.
It is an object of the present invention to provide a semiconductor chip pick-up method capable of picking up a semiconductor chip formed by dividing a semiconductor wafer without damaging them, and, as required, picking up a plurality of divided semiconductor chips en bloc.
To attain the above object, according to the present invention, there is provided a method of picking up a plurality of semiconductor chips formed by dividing a semiconductor wafer, comprising:
the semiconductor chip holding step of adhesively holding the plurality of semiconductor chips on an elastic adhesive pad which has innumerable pores formed in the surface and generates adhesive force when negative pressure is produced by the pores crushed by restoration force generated by elasticity and adhesion; and
the semiconductor chip picking up step of picking up the semiconductor chips in a state of air in the pores being expanded by heating the elastic adhesive pad which adhesively holds the plurality of semiconductor chips, at a predetermined temperature.
According to the present invention, there is also provided a method of picking up a plurality of semiconductor chips formed by dividing a semiconductor wafer by forming cutting grooves having a predetermined depth in the surface of the semiconductor wafer, affixing a protective tape to the surface having the cutting grooves formed therein and grinding the back surface of the semiconductor wafer until the cutting grooves are exposed, comprising:
the semiconductor chip holding step of adhesively holding the plurality of semiconductor chips on an elastic adhesive pad which has innumerable pores formed in the surface and generates adhesive force when negative pressure is produced by the pores crushed by restoration force generated by elasticity and adhesion, by putting the ground surfaces of the plurality of semiconductor chips, to which the protective tape has been affixed, onto the elastic adhesive pad;
the protective tape separating step of separating the protective tape affixed to the semiconductor chips in a state of the plurality of semiconductor chips being adhesively held on the elastic adhesive pad; and
the semiconductor chip picking up step of picking up the semiconductor chips in a state of air in the pores being expanded by heating the elastic adhesive pad which adhesively holds the plurality of semiconductor chips, at a predetermined temperature.
The above semiconductor chip holding step desirably includes the step of stretching the above protective tape to broaden the interval between adjacent semiconductor chips.